What do you need it to do exactly? You have a probe that will detect the top of the work and set Z DRO to a preset value?

I've just been working on this for my router, based heavily on code published elsewhere (including 53 pages of posts on CNCZone in just one topic, making sure that I had the latest version...). It's pretty straightforward, Just a couple of lines of code to do the work. Plus a couple of dozen lines to sort out issues like units, abs/inc mode, coord display mode, etc...

Be happy to throw something together if you really can't find what you want elsewhere but I would suggest that you pick up a known version from CNCZone - worth signing up to it for that alone.